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vpe.c

/*
 * Copyright (C) 2004, 2005 MIPS Technologies, Inc.  All rights reserved.
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 */

/*
 * VPE support module
 *
 * Provides support for loading a MIPS SP program on VPE1.
 * The SP enviroment is rather simple, no tlb's.  It needs to be relocatable
 * (or partially linked). You should initialise your stack in the startup
 * code. This loader looks for the symbol __start and sets up
 * execution to resume from there. The MIPS SDE kit contains suitable examples.
 *
 * To load and run, simply cat a SP 'program file' to /dev/vpe1.
 * i.e cat spapp >/dev/vpe1.
 */
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <linux/elf.h>
#include <linux/seq_file.h>
#include <linux/smp_lock.h>
#include <linux/syscalls.h>
#include <linux/moduleloader.h>
#include <linux/interrupt.h>
#include <linux/poll.h>
#include <linux/bootmem.h>
#include <asm/mipsregs.h>
#include <asm/mipsmtregs.h>
#include <asm/cacheflush.h>
#include <asm/atomic.h>
#include <asm/cpu.h>
#include <asm/mips_mt.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/vpe.h>
#include <asm/kspd.h>

typedef void *vpe_handle;

#ifndef ARCH_SHF_SMALL
#define ARCH_SHF_SMALL 0
#endif

/* If this is set, the section belongs in the init part of the module */
#define INIT_OFFSET_MASK (1UL << (BITS_PER_LONG-1))

/*
 * The number of TCs and VPEs physically available on the core
 */
static int hw_tcs, hw_vpes;
static char module_name[] = "vpe";
static int major;
static const int minor = 1;   /* fixed for now  */

#ifdef CONFIG_MIPS_APSP_KSPD
 static struct kspd_notifications kspd_events;
static int kspd_events_reqd = 0;
#endif

/* grab the likely amount of memory we will need. */
#ifdef CONFIG_MIPS_VPE_LOADER_TOM
#define P_SIZE (2 * 1024 * 1024)
#else
/* add an overhead to the max kmalloc size for non-striped symbols/etc */
#define P_SIZE (256 * 1024)
#endif

extern unsigned long physical_memsize;

#define MAX_VPES 16
#define VPE_PATH_MAX 256

enum vpe_state {
      VPE_STATE_UNUSED = 0,
      VPE_STATE_INUSE,
      VPE_STATE_RUNNING
};

enum tc_state {
      TC_STATE_UNUSED = 0,
      TC_STATE_INUSE,
      TC_STATE_RUNNING,
      TC_STATE_DYNAMIC
};

struct vpe {
      enum vpe_state state;

      /* (device) minor associated with this vpe */
      int minor;

      /* elfloader stuff */
      void *load_addr;
      unsigned long len;
      char *pbuffer;
      unsigned long plen;
      unsigned int uid, gid;
      char cwd[VPE_PATH_MAX];

      unsigned long __start;

      /* tc's associated with this vpe */
      struct list_head tc;

      /* The list of vpe's */
      struct list_head list;

      /* shared symbol address */
      void *shared_ptr;

      /* the list of who wants to know when something major happens */
      struct list_head notify;

      unsigned int ntcs;
};

struct tc {
      enum tc_state state;
      int index;

      struct vpe *pvpe; /* parent VPE */
      struct list_head tc;    /* The list of TC's with this VPE */
      struct list_head list;  /* The global list of tc's */
};

struct {
      /* Virtual processing elements */
      struct list_head vpe_list;

      /* Thread contexts */
      struct list_head tc_list;
} vpecontrol = {
      .vpe_list = LIST_HEAD_INIT(vpecontrol.vpe_list),
      .tc_list = LIST_HEAD_INIT(vpecontrol.tc_list)
};

static void release_progmem(void *ptr);
extern void save_gp_address(unsigned int secbase, unsigned int rel);

/* get the vpe associated with this minor */
struct vpe *get_vpe(int minor)
{
      struct vpe *v;

      if (!cpu_has_mipsmt)
            return NULL;

      list_for_each_entry(v, &vpecontrol.vpe_list, list) {
            if (v->minor == minor)
                  return v;
      }

      return NULL;
}

/* get the vpe associated with this minor */
struct tc *get_tc(int index)
{
      struct tc *t;

      list_for_each_entry(t, &vpecontrol.tc_list, list) {
            if (t->index == index)
                  return t;
      }

      return NULL;
}

struct tc *get_tc_unused(void)
{
      struct tc *t;

      list_for_each_entry(t, &vpecontrol.tc_list, list) {
            if (t->state == TC_STATE_UNUSED)
                  return t;
      }

      return NULL;
}

/* allocate a vpe and associate it with this minor (or index) */
struct vpe *alloc_vpe(int minor)
{
      struct vpe *v;

      if ((v = kzalloc(sizeof(struct vpe), GFP_KERNEL)) == NULL) {
            return NULL;
      }

      INIT_LIST_HEAD(&v->tc);
      list_add_tail(&v->list, &vpecontrol.vpe_list);

      INIT_LIST_HEAD(&v->notify);
      v->minor = minor;
      return v;
}

/* allocate a tc. At startup only tc0 is running, all other can be halted. */
struct tc *alloc_tc(int index)
{
      struct tc *tc;

      if ((tc = kzalloc(sizeof(struct tc), GFP_KERNEL)) == NULL)
            goto out;

      INIT_LIST_HEAD(&tc->tc);
      tc->index = index;
      list_add_tail(&tc->list, &vpecontrol.tc_list);

out:
      return tc;
}

/* clean up and free everything */
void release_vpe(struct vpe *v)
{
      list_del(&v->list);
      if (v->load_addr)
            release_progmem(v);
      kfree(v);
}

void dump_mtregs(void)
{
      unsigned long val;

      val = read_c0_config3();
      printk("config3 0x%lx MT %ld\n", val,
             (val & CONFIG3_MT) >> CONFIG3_MT_SHIFT);

      val = read_c0_mvpcontrol();
      printk("MVPControl 0x%lx, STLB %ld VPC %ld EVP %ld\n", val,
             (val & MVPCONTROL_STLB) >> MVPCONTROL_STLB_SHIFT,
             (val & MVPCONTROL_VPC) >> MVPCONTROL_VPC_SHIFT,
             (val & MVPCONTROL_EVP));

      val = read_c0_mvpconf0();
      printk("mvpconf0 0x%lx, PVPE %ld PTC %ld M %ld\n", val,
             (val & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT,
             val & MVPCONF0_PTC, (val & MVPCONF0_M) >> MVPCONF0_M_SHIFT);
}

/* Find some VPE program space  */
static void *alloc_progmem(unsigned long len)
{
      void *addr;

#ifdef CONFIG_MIPS_VPE_LOADER_TOM
      /*
       * This means you must tell Linux to use less memory than you
       * physically have, for example by passing a mem= boot argument.
       */
      addr = pfn_to_kaddr(max_low_pfn);
      memset(addr, 0, len);
#else
      /* simple grab some mem for now */
      addr = kzalloc(len, GFP_KERNEL);
#endif

      return addr;
}

static void release_progmem(void *ptr)
{
#ifndef CONFIG_MIPS_VPE_LOADER_TOM
      kfree(ptr);
#endif
}

/* Update size with this section: return offset. */
static long get_offset(unsigned long *size, Elf_Shdr * sechdr)
{
      long ret;

      ret = ALIGN(*size, sechdr->sh_addralign ? : 1);
      *size = ret + sechdr->sh_size;
      return ret;
}

/* Lay out the SHF_ALLOC sections in a way not dissimilar to how ld
   might -- code, read-only data, read-write data, small data.  Tally
   sizes, and place the offsets into sh_entsize fields: high bit means it
   belongs in init. */
static void layout_sections(struct module *mod, const Elf_Ehdr * hdr,
                      Elf_Shdr * sechdrs, const char *secstrings)
{
      static unsigned long const masks[][2] = {
            /* NOTE: all executable code must be the first section
             * in this array; otherwise modify the text_size
             * finder in the two loops below */
            {SHF_EXECINSTR | SHF_ALLOC, ARCH_SHF_SMALL},
            {SHF_ALLOC, SHF_WRITE | ARCH_SHF_SMALL},
            {SHF_WRITE | SHF_ALLOC, ARCH_SHF_SMALL},
            {ARCH_SHF_SMALL | SHF_ALLOC, 0}
      };
      unsigned int m, i;

      for (i = 0; i < hdr->e_shnum; i++)
            sechdrs[i].sh_entsize = ~0UL;

      for (m = 0; m < ARRAY_SIZE(masks); ++m) {
            for (i = 0; i < hdr->e_shnum; ++i) {
                  Elf_Shdr *s = &sechdrs[i];

                  //  || strncmp(secstrings + s->sh_name, ".init", 5) == 0)
                  if ((s->sh_flags & masks[m][0]) != masks[m][0]
                      || (s->sh_flags & masks[m][1])
                      || s->sh_entsize != ~0UL)
                        continue;
                  s->sh_entsize = get_offset(&mod->core_size, s);
            }

            if (m == 0)
                  mod->core_text_size = mod->core_size;

      }
}


/* from module-elf32.c, but subverted a little */

struct mips_hi16 {
      struct mips_hi16 *next;
      Elf32_Addr *addr;
      Elf32_Addr value;
};

static struct mips_hi16 *mips_hi16_list;
static unsigned int gp_offs, gp_addr;

static int apply_r_mips_none(struct module *me, uint32_t *location,
                       Elf32_Addr v)
{
      return 0;
}

static int apply_r_mips_gprel16(struct module *me, uint32_t *location,
                        Elf32_Addr v)
{
      int rel;

      if( !(*location & 0xffff) ) {
            rel = (int)v - gp_addr;
      }
      else {
            /* .sbss + gp(relative) + offset */
            /* kludge! */
            rel =  (int)(short)((int)v + gp_offs +
                            (int)(short)(*location & 0xffff) - gp_addr);
      }

      if( (rel > 32768) || (rel < -32768) ) {
            printk(KERN_DEBUG "VPE loader: apply_r_mips_gprel16: "
                   "relative address 0x%x out of range of gp register\n",
                   rel);
            return -ENOEXEC;
      }

      *location = (*location & 0xffff0000) | (rel & 0xffff);

      return 0;
}

static int apply_r_mips_pc16(struct module *me, uint32_t *location,
                       Elf32_Addr v)
{
      int rel;
      rel = (((unsigned int)v - (unsigned int)location));
      rel >>= 2;        // because the offset is in _instructions_ not bytes.
      rel -= 1;         // and one instruction less due to the branch delay slot.

      if( (rel > 32768) || (rel < -32768) ) {
            printk(KERN_DEBUG "VPE loader: "
                   "apply_r_mips_pc16: relative address out of range 0x%x\n", rel);
            return -ENOEXEC;
      }

      *location = (*location & 0xffff0000) | (rel & 0xffff);

      return 0;
}

static int apply_r_mips_32(struct module *me, uint32_t *location,
                     Elf32_Addr v)
{
      *location += v;

      return 0;
}

static int apply_r_mips_26(struct module *me, uint32_t *location,
                     Elf32_Addr v)
{
      if (v % 4) {
            printk(KERN_DEBUG "VPE loader: apply_r_mips_26 "
                   " unaligned relocation\n");
            return -ENOEXEC;
      }

/*
 * Not desperately convinced this is a good check of an overflow condition
 * anyway. But it gets in the way of handling undefined weak symbols which
 * we want to set to zero.
 * if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
 * printk(KERN_ERR
 * "module %s: relocation overflow\n",
 * me->name);
 * return -ENOEXEC;
 * }
 */

      *location = (*location & ~0x03ffffff) |
            ((*location + (v >> 2)) & 0x03ffffff);
      return 0;
}

static int apply_r_mips_hi16(struct module *me, uint32_t *location,
                       Elf32_Addr v)
{
      struct mips_hi16 *n;

      /*
       * We cannot relocate this one now because we don't know the value of
       * the carry we need to add.  Save the information, and let LO16 do the
       * actual relocation.
       */
      n = kmalloc(sizeof *n, GFP_KERNEL);
      if (!n)
            return -ENOMEM;

      n->addr = location;
      n->value = v;
      n->next = mips_hi16_list;
      mips_hi16_list = n;

      return 0;
}

static int apply_r_mips_lo16(struct module *me, uint32_t *location,
                       Elf32_Addr v)
{
      unsigned long insnlo = *location;
      Elf32_Addr val, vallo;

      /* Sign extend the addend we extract from the lo insn.  */
      vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;

      if (mips_hi16_list != NULL) {
            struct mips_hi16 *l;

            l = mips_hi16_list;
            while (l != NULL) {
                  struct mips_hi16 *next;
                  unsigned long insn;

                  /*
                   * The value for the HI16 had best be the same.
                   */
                  if (v != l->value) {
                        printk(KERN_DEBUG "VPE loader: "
                               "apply_r_mips_lo16/hi16: \t"
                               "inconsistent value information\n");
                        return -ENOEXEC;
                  }

                  /*
                   * Do the HI16 relocation.  Note that we actually don't
                   * need to know anything about the LO16 itself, except
                   * where to find the low 16 bits of the addend needed
                   * by the LO16.
                   */
                  insn = *l->addr;
                  val = ((insn & 0xffff) << 16) + vallo;
                  val += v;

                  /*
                   * Account for the sign extension that will happen in
                   * the low bits.
                   */
                  val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;

                  insn = (insn & ~0xffff) | val;
                  *l->addr = insn;

                  next = l->next;
                  kfree(l);
                  l = next;
            }

            mips_hi16_list = NULL;
      }

      /*
       * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
       */
      val = v + vallo;
      insnlo = (insnlo & ~0xffff) | (val & 0xffff);
      *location = insnlo;

      return 0;
}

static int (*reloc_handlers[]) (struct module *me, uint32_t *location,
                        Elf32_Addr v) = {
      [R_MIPS_NONE]     = apply_r_mips_none,
      [R_MIPS_32] = apply_r_mips_32,
      [R_MIPS_26] = apply_r_mips_26,
      [R_MIPS_HI16]     = apply_r_mips_hi16,
      [R_MIPS_LO16]     = apply_r_mips_lo16,
      [R_MIPS_GPREL16] = apply_r_mips_gprel16,
      [R_MIPS_PC16] = apply_r_mips_pc16
};

static char *rstrs[] = {
      [R_MIPS_NONE]     = "MIPS_NONE",
      [R_MIPS_32] = "MIPS_32",
      [R_MIPS_26] = "MIPS_26",
      [R_MIPS_HI16]     = "MIPS_HI16",
      [R_MIPS_LO16]     = "MIPS_LO16",
      [R_MIPS_GPREL16] = "MIPS_GPREL16",
      [R_MIPS_PC16] = "MIPS_PC16"
};

int apply_relocations(Elf32_Shdr *sechdrs,
                  const char *strtab,
                  unsigned int symindex,
                  unsigned int relsec,
                  struct module *me)
{
      Elf32_Rel *rel = (void *) sechdrs[relsec].sh_addr;
      Elf32_Sym *sym;
      uint32_t *location;
      unsigned int i;
      Elf32_Addr v;
      int res;

      for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
            Elf32_Word r_info = rel[i].r_info;

            /* This is where to make the change */
            location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
                  + rel[i].r_offset;
            /* This is the symbol it is referring to */
            sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
                  + ELF32_R_SYM(r_info);

            if (!sym->st_value) {
                  printk(KERN_DEBUG "%s: undefined weak symbol %s\n",
                         me->name, strtab + sym->st_name);
                  /* just print the warning, dont barf */
            }

            v = sym->st_value;

            res = reloc_handlers[ELF32_R_TYPE(r_info)](me, location, v);
            if( res ) {
                  char *r = rstrs[ELF32_R_TYPE(r_info)];
                  printk(KERN_WARNING "VPE loader: .text+0x%x "
                         "relocation type %s for symbol \"%s\" failed\n",
                         rel[i].r_offset, r ? r : "UNKNOWN",
                         strtab + sym->st_name);
                  return res;
            }
      }

      return 0;
}

void save_gp_address(unsigned int secbase, unsigned int rel)
{
      gp_addr = secbase + rel;
      gp_offs = gp_addr - (secbase & 0xffff0000);
}
/* end module-elf32.c */



/* Change all symbols so that sh_value encodes the pointer directly. */
static void simplify_symbols(Elf_Shdr * sechdrs,
                      unsigned int symindex,
                      const char *strtab,
                      const char *secstrings,
                      unsigned int nsecs, struct module *mod)
{
      Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
      unsigned long secbase, bssbase = 0;
      unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
      int size;

      /* find the .bss section for COMMON symbols */
      for (i = 0; i < nsecs; i++) {
            if (strncmp(secstrings + sechdrs[i].sh_name, ".bss", 4) == 0) {
                  bssbase = sechdrs[i].sh_addr;
                  break;
            }
      }

      for (i = 1; i < n; i++) {
            switch (sym[i].st_shndx) {
            case SHN_COMMON:
                  /* Allocate space for the symbol in the .bss section.
                     st_value is currently size.
                     We want it to have the address of the symbol. */

                  size = sym[i].st_value;
                  sym[i].st_value = bssbase;

                  bssbase += size;
                  break;

            case SHN_ABS:
                  /* Don't need to do anything */
                  break;

            case SHN_UNDEF:
                  /* ret = -ENOENT; */
                  break;

            case SHN_MIPS_SCOMMON:
                  printk(KERN_DEBUG "simplify_symbols: ignoring SHN_MIPS_SCOMMON "
                         "symbol <%s> st_shndx %d\n", strtab + sym[i].st_name,
                         sym[i].st_shndx);
                  // .sbss section
                  break;

            default:
                  secbase = sechdrs[sym[i].st_shndx].sh_addr;

                  if (strncmp(strtab + sym[i].st_name, "_gp", 3) == 0) {
                        save_gp_address(secbase, sym[i].st_value);
                  }

                  sym[i].st_value += secbase;
                  break;
            }
      }
}

#ifdef DEBUG_ELFLOADER
static void dump_elfsymbols(Elf_Shdr * sechdrs, unsigned int symindex,
                      const char *strtab, struct module *mod)
{
      Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
      unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);

      printk(KERN_DEBUG "dump_elfsymbols: n %d\n", n);
      for (i = 1; i < n; i++) {
            printk(KERN_DEBUG " i %d name <%s> 0x%x\n", i,
                   strtab + sym[i].st_name, sym[i].st_value);
      }
}
#endif

/* We are prepared so configure and start the VPE... */
static int vpe_run(struct vpe * v)
{
      unsigned long flags, val, dmt_flag;
      struct vpe_notifications *n;
      unsigned int vpeflags;
      struct tc *t;

      /* check we are the Master VPE */
      local_irq_save(flags);
      val = read_c0_vpeconf0();
      if (!(val & VPECONF0_MVP)) {
            printk(KERN_WARNING
                   "VPE loader: only Master VPE's are allowed to configure MT\n");
            local_irq_restore(flags);

            return -1;
      }

      dmt_flag = dmt();
      vpeflags = dvpe();

      if (!list_empty(&v->tc)) {
            if ((t = list_entry(v->tc.next, struct tc, tc)) == NULL) {
                  evpe(vpeflags);
                  emt(dmt_flag);
                  local_irq_restore(flags);

                  printk(KERN_WARNING
                         "VPE loader: TC %d is already in use.\n",
                               t->index);
                  return -ENOEXEC;
            }
      } else {
            evpe(vpeflags);
            emt(dmt_flag);
            local_irq_restore(flags);

            printk(KERN_WARNING
                   "VPE loader: No TC's associated with VPE %d\n",
                   v->minor);

            return -ENOEXEC;
      }

      /* Put MVPE's into 'configuration state' */
      set_c0_mvpcontrol(MVPCONTROL_VPC);

      settc(t->index);

      /* should check it is halted, and not activated */
      if ((read_tc_c0_tcstatus() & TCSTATUS_A) || !(read_tc_c0_tchalt() & TCHALT_H)) {
            evpe(vpeflags);
            emt(dmt_flag);
            local_irq_restore(flags);

            printk(KERN_WARNING "VPE loader: TC %d is already active!\n",
                   t->index);

            return -ENOEXEC;
      }

      /* Write the address we want it to start running from in the TCPC register. */
      write_tc_c0_tcrestart((unsigned long)v->__start);
      write_tc_c0_tccontext((unsigned long)0);

      /*
       * Mark the TC as activated, not interrupt exempt and not dynamically
       * allocatable
       */
      val = read_tc_c0_tcstatus();
      val = (val & ~(TCSTATUS_DA | TCSTATUS_IXMT)) | TCSTATUS_A;
      write_tc_c0_tcstatus(val);

      write_tc_c0_tchalt(read_tc_c0_tchalt() & ~TCHALT_H);

      /*
       * The sde-kit passes 'memsize' to __start in $a3, so set something
       * here...  Or set $a3 to zero and define DFLT_STACK_SIZE and
       * DFLT_HEAP_SIZE when you compile your program
       */
      mttgpr(6, v->ntcs);
      mttgpr(7, physical_memsize);

      /* set up VPE1 */
      /*
       * bind the TC to VPE 1 as late as possible so we only have the final
       * VPE registers to set up, and so an EJTAG probe can trigger on it
       */
      write_tc_c0_tcbind((read_tc_c0_tcbind() & ~TCBIND_CURVPE) | 1);

      write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~(VPECONF0_VPA));

      back_to_back_c0_hazard();

      /* Set up the XTC bit in vpeconf0 to point at our tc */
      write_vpe_c0_vpeconf0( (read_vpe_c0_vpeconf0() & ~(VPECONF0_XTC))
                            | (t->index << VPECONF0_XTC_SHIFT));

      back_to_back_c0_hazard();

      /* enable this VPE */
      write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() | VPECONF0_VPA);

      /* clear out any left overs from a previous program */
      write_vpe_c0_status(0);
      write_vpe_c0_cause(0);

      /* take system out of configuration state */
      clear_c0_mvpcontrol(MVPCONTROL_VPC);

      /*
       * SMTC/SMVP kernels manage VPE enable independently,
       * but uniprocessor kernels need to turn it on, even
       * if that wasn't the pre-dvpe() state.
       */
#ifdef CONFIG_SMP
      evpe(vpeflags);
#else
      evpe(EVPE_ENABLE);
#endif
      emt(dmt_flag);
      local_irq_restore(flags);

      list_for_each_entry(n, &v->notify, list)
            n->start(minor);

      return 0;
}

static int find_vpe_symbols(struct vpe * v, Elf_Shdr * sechdrs,
                              unsigned int symindex, const char *strtab,
                              struct module *mod)
{
      Elf_Sym *sym = (void *)sechdrs[symindex].sh_addr;
      unsigned int i, n = sechdrs[symindex].sh_size / sizeof(Elf_Sym);

      for (i = 1; i < n; i++) {
            if (strcmp(strtab + sym[i].st_name, "__start") == 0) {
                  v->__start = sym[i].st_value;
            }

            if (strcmp(strtab + sym[i].st_name, "vpe_shared") == 0) {
                  v->shared_ptr = (void *)sym[i].st_value;
            }
      }

      if ( (v->__start == 0) || (v->shared_ptr == NULL))
            return -1;

      return 0;
}

/*
 * Allocates a VPE with some program code space(the load address), copies the
 * contents of the program (p)buffer performing relocatations/etc, free's it
 * when finished.
 */
static int vpe_elfload(struct vpe * v)
{
      Elf_Ehdr *hdr;
      Elf_Shdr *sechdrs;
      long err = 0;
      char *secstrings, *strtab = NULL;
      unsigned int len, i, symindex = 0, strindex = 0, relocate = 0;
      struct module mod;      // so we can re-use the relocations code

      memset(&mod, 0, sizeof(struct module));
      strcpy(mod.name, "VPE loader");

      hdr = (Elf_Ehdr *) v->pbuffer;
      len = v->plen;

      /* Sanity checks against insmoding binaries or wrong arch,
         weird elf version */
      if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
          || (hdr->e_type != ET_REL && hdr->e_type != ET_EXEC)
          || !elf_check_arch(hdr)
          || hdr->e_shentsize != sizeof(*sechdrs)) {
            printk(KERN_WARNING
                   "VPE loader: program wrong arch or weird elf version\n");

            return -ENOEXEC;
      }

      if (hdr->e_type == ET_REL)
            relocate = 1;

      if (len < hdr->e_shoff + hdr->e_shnum * sizeof(Elf_Shdr)) {
            printk(KERN_ERR "VPE loader: program length %u truncated\n",
                   len);

            return -ENOEXEC;
      }

      /* Convenience variables */
      sechdrs = (void *)hdr + hdr->e_shoff;
      secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
      sechdrs[0].sh_addr = 0;

      /* And these should exist, but gcc whinges if we don't init them */
      symindex = strindex = 0;

      if (relocate) {
            for (i = 1; i < hdr->e_shnum; i++) {
                  if (sechdrs[i].sh_type != SHT_NOBITS
                      && len < sechdrs[i].sh_offset + sechdrs[i].sh_size) {
                        printk(KERN_ERR "VPE program length %u truncated\n",
                               len);
                        return -ENOEXEC;
                  }

                  /* Mark all sections sh_addr with their address in the
                     temporary image. */
                  sechdrs[i].sh_addr = (size_t) hdr + sechdrs[i].sh_offset;

                  /* Internal symbols and strings. */
                  if (sechdrs[i].sh_type == SHT_SYMTAB) {
                        symindex = i;
                        strindex = sechdrs[i].sh_link;
                        strtab = (char *)hdr + sechdrs[strindex].sh_offset;
                  }
            }
            layout_sections(&mod, hdr, sechdrs, secstrings);
      }

      v->load_addr = alloc_progmem(mod.core_size);
      if (!v->load_addr)
            return -ENOMEM;

      pr_info("VPE loader: loading to %p\n", v->load_addr);

      if (relocate) {
            for (i = 0; i < hdr->e_shnum; i++) {
                  void *dest;

                  if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;

                  dest = v->load_addr + sechdrs[i].sh_entsize;

                  if (sechdrs[i].sh_type != SHT_NOBITS)
                        memcpy(dest, (void *)sechdrs[i].sh_addr,
                               sechdrs[i].sh_size);
                  /* Update sh_addr to point to copy in image. */
                  sechdrs[i].sh_addr = (unsigned long)dest;

                  printk(KERN_DEBUG " section sh_name %s sh_addr 0x%x\n",
                         secstrings + sechdrs[i].sh_name, sechdrs[i].sh_addr);
            }

            /* Fix up syms, so that st_value is a pointer to location. */
            simplify_symbols(sechdrs, symindex, strtab, secstrings,
                         hdr->e_shnum, &mod);

            /* Now do relocations. */
            for (i = 1; i < hdr->e_shnum; i++) {
                  const char *strtab = (char *)sechdrs[strindex].sh_addr;
                  unsigned int info = sechdrs[i].sh_info;

                  /* Not a valid relocation section? */
                  if (info >= hdr->e_shnum)
                        continue;

                  /* Don't bother with non-allocated sections */
                  if (!(sechdrs[info].sh_flags & SHF_ALLOC))
                        continue;

                  if (sechdrs[i].sh_type == SHT_REL)
                        err = apply_relocations(sechdrs, strtab, symindex, i,
                                          &mod);
                  else if (sechdrs[i].sh_type == SHT_RELA)
                        err = apply_relocate_add(sechdrs, strtab, symindex, i,
                                           &mod);
                  if (err < 0)
                        return err;

            }
      } else {
            struct elf_phdr *phdr = (struct elf_phdr *) ((char *)hdr + hdr->e_phoff);

            for (i = 0; i < hdr->e_phnum; i++) {
                  if (phdr->p_type == PT_LOAD) {
                        memcpy((void *)phdr->p_paddr,
                               (char *)hdr + phdr->p_offset,
                               phdr->p_filesz);
                        memset((void *)phdr->p_paddr + phdr->p_filesz,
                               0, phdr->p_memsz - phdr->p_filesz);
                }
                phdr++;
            }

            for (i = 0; i < hdr->e_shnum; i++) {
                  /* Internal symbols and strings. */
                  if (sechdrs[i].sh_type == SHT_SYMTAB) {
                        symindex = i;
                        strindex = sechdrs[i].sh_link;
                        strtab = (char *)hdr + sechdrs[strindex].sh_offset;

                        /* mark the symtab's address for when we try to find the
                           magic symbols */
                        sechdrs[i].sh_addr = (size_t) hdr + sechdrs[i].sh_offset;
                  }
            }
      }

      /* make sure it's physically written out */
      flush_icache_range((unsigned long)v->load_addr,
                     (unsigned long)v->load_addr + v->len);

      if ((find_vpe_symbols(v, sechdrs, symindex, strtab, &mod)) < 0) {
            if (v->__start == 0) {
                  printk(KERN_WARNING "VPE loader: program does not contain "
                         "a __start symbol\n");
                  return -ENOEXEC;
            }

            if (v->shared_ptr == NULL)
                  printk(KERN_WARNING "VPE loader: "
                         "program does not contain vpe_shared symbol.\n"
                         " Unable to use AMVP (AP/SP) facilities.\n");
      }

      printk(" elf loaded\n");
      return 0;
}

static void cleanup_tc(struct tc *tc)
{
      unsigned long flags;
      unsigned int mtflags, vpflags;
      int tmp;

      local_irq_save(flags);
      mtflags = dmt();
      vpflags = dvpe();
      /* Put MVPE's into 'configuration state' */
      set_c0_mvpcontrol(MVPCONTROL_VPC);

      settc(tc->index);
      tmp = read_tc_c0_tcstatus();

      /* mark not allocated and not dynamically allocatable */
      tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
      tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
      write_tc_c0_tcstatus(tmp);

      write_tc_c0_tchalt(TCHALT_H);
      mips_ihb();

      /* bind it to anything other than VPE1 */
//    write_tc_c0_tcbind(read_tc_c0_tcbind() & ~TCBIND_CURVPE); // | TCBIND_CURVPE

      clear_c0_mvpcontrol(MVPCONTROL_VPC);
      evpe(vpflags);
      emt(mtflags);
      local_irq_restore(flags);
}

static int getcwd(char *buff, int size)
{
      mm_segment_t old_fs;
      int ret;

      old_fs = get_fs();
      set_fs(KERNEL_DS);

      ret = sys_getcwd(buff, size);

      set_fs(old_fs);

      return ret;
}

/* checks VPE is unused and gets ready to load program  */
static int vpe_open(struct inode *inode, struct file *filp)
{
      enum vpe_state state;
      struct vpe_notifications *not;
      struct vpe *v;
      int ret, err = 0;

      lock_kernel();
      if (minor != iminor(inode)) {
            /* assume only 1 device at the moment. */
            printk(KERN_WARNING "VPE loader: only vpe1 is supported\n");
            err = -ENODEV;
            goto out;
      }

      if ((v = get_vpe(tclimit)) == NULL) {
            printk(KERN_WARNING "VPE loader: unable to get vpe\n");
            err = -ENODEV;
            goto out;
      }

      state = xchg(&v->state, VPE_STATE_INUSE);
      if (state != VPE_STATE_UNUSED) {
            printk(KERN_DEBUG "VPE loader: tc in use dumping regs\n");

            list_for_each_entry(not, &v->notify, list) {
                  not->stop(tclimit);
            }

            release_progmem(v->load_addr);
            cleanup_tc(get_tc(tclimit));
      }

      /* this of-course trashes what was there before... */
      v->pbuffer = vmalloc(P_SIZE);
      v->plen = P_SIZE;
      v->load_addr = NULL;
      v->len = 0;

      v->uid = filp->f_uid;
      v->gid = filp->f_gid;

#ifdef CONFIG_MIPS_APSP_KSPD
      /* get kspd to tell us when a syscall_exit happens */
      if (!kspd_events_reqd) {
            kspd_notify(&kspd_events);
            kspd_events_reqd++;
      }
#endif

      v->cwd[0] = 0;
      ret = getcwd(v->cwd, VPE_PATH_MAX);
      if (ret < 0)
            printk(KERN_WARNING "VPE loader: open, getcwd returned %d\n", ret);

      v->shared_ptr = NULL;
      v->__start = 0;

out:
      unlock_kernel();
      return 0;
}

static int vpe_release(struct inode *inode, struct file *filp)
{
      struct vpe *v;
      Elf_Ehdr *hdr;
      int ret = 0;

      v = get_vpe(tclimit);
      if (v == NULL)
            return -ENODEV;

      hdr = (Elf_Ehdr *) v->pbuffer;
      if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) == 0) {
            if (vpe_elfload(v) >= 0) {
                  vpe_run(v);
            } else {
                  printk(KERN_WARNING "VPE loader: ELF load failed.\n");
                  ret = -ENOEXEC;
            }
      } else {
            printk(KERN_WARNING "VPE loader: only elf files are supported\n");
            ret = -ENOEXEC;
      }

      /* It's good to be able to run the SP and if it chokes have a look at
         the /dev/rt?. But if we reset the pointer to the shared struct we
         loose what has happened. So perhaps if garbage is sent to the vpe
         device, use it as a trigger for the reset. Hopefully a nice
         executable will be along shortly. */
      if (ret < 0)
            v->shared_ptr = NULL;

      // cleanup any temp buffers
      if (v->pbuffer)
            vfree(v->pbuffer);
      v->plen = 0;
      return ret;
}

static ssize_t vpe_write(struct file *file, const char __user * buffer,
                   size_t count, loff_t * ppos)
{
      size_t ret = count;
      struct vpe *v;

      if (iminor(file->f_path.dentry->d_inode) != minor)
            return -ENODEV;

      v = get_vpe(tclimit);
      if (v == NULL)
            return -ENODEV;

      if (v->pbuffer == NULL) {
            printk(KERN_ERR "VPE loader: no buffer for program\n");
            return -ENOMEM;
      }

      if ((count + v->len) > v->plen) {
            printk(KERN_WARNING
                   "VPE loader: elf size too big. Perhaps strip uneeded symbols\n");
            return -ENOMEM;
      }

      count -= copy_from_user(v->pbuffer + v->len, buffer, count);
      if (!count)
            return -EFAULT;

      v->len += count;
      return ret;
}

static const struct file_operations vpe_fops = {
      .owner = THIS_MODULE,
      .open = vpe_open,
      .release = vpe_release,
      .write = vpe_write
};

/* module wrapper entry points */
/* give me a vpe */
vpe_handle vpe_alloc(void)
{
      int i;
      struct vpe *v;

      /* find a vpe */
      for (i = 1; i < MAX_VPES; i++) {
            if ((v = get_vpe(i)) != NULL) {
                  v->state = VPE_STATE_INUSE;
                  return v;
            }
      }
      return NULL;
}

EXPORT_SYMBOL(vpe_alloc);

/* start running from here */
int vpe_start(vpe_handle vpe, unsigned long start)
{
      struct vpe *v = vpe;

      v->__start = start;
      return vpe_run(v);
}

EXPORT_SYMBOL(vpe_start);

/* halt it for now */
int vpe_stop(vpe_handle vpe)
{
      struct vpe *v = vpe;
      struct tc *t;
      unsigned int evpe_flags;

      evpe_flags = dvpe();

      if ((t = list_entry(v->tc.next, struct tc, tc)) != NULL) {

            settc(t->index);
            write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);
      }

      evpe(evpe_flags);

      return 0;
}

EXPORT_SYMBOL(vpe_stop);

/* I've done with it thank you */
int vpe_free(vpe_handle vpe)
{
      struct vpe *v = vpe;
      struct tc *t;
      unsigned int evpe_flags;

      if ((t = list_entry(v->tc.next, struct tc, tc)) == NULL) {
            return -ENOEXEC;
      }

      evpe_flags = dvpe();

      /* Put MVPE's into 'configuration state' */
      set_c0_mvpcontrol(MVPCONTROL_VPC);

      settc(t->index);
      write_vpe_c0_vpeconf0(read_vpe_c0_vpeconf0() & ~VPECONF0_VPA);

      /* halt the TC */
      write_tc_c0_tchalt(TCHALT_H);
      mips_ihb();

      /* mark the TC unallocated */
      write_tc_c0_tcstatus(read_tc_c0_tcstatus() & ~TCSTATUS_A);

      v->state = VPE_STATE_UNUSED;

      clear_c0_mvpcontrol(MVPCONTROL_VPC);
      evpe(evpe_flags);

      return 0;
}

EXPORT_SYMBOL(vpe_free);

void *vpe_get_shared(int index)
{
      struct vpe *v;

      if ((v = get_vpe(index)) == NULL)
            return NULL;

      return v->shared_ptr;
}

EXPORT_SYMBOL(vpe_get_shared);

int vpe_getuid(int index)
{
      struct vpe *v;

      if ((v = get_vpe(index)) == NULL)
            return -1;

      return v->uid;
}

EXPORT_SYMBOL(vpe_getuid);

int vpe_getgid(int index)
{
      struct vpe *v;

      if ((v = get_vpe(index)) == NULL)
            return -1;

      return v->gid;
}

EXPORT_SYMBOL(vpe_getgid);

int vpe_notify(int index, struct vpe_notifications *notify)
{
      struct vpe *v;

      if ((v = get_vpe(index)) == NULL)
            return -1;

      list_add(&notify->list, &v->notify);
      return 0;
}

EXPORT_SYMBOL(vpe_notify);

char *vpe_getcwd(int index)
{
      struct vpe *v;

      if ((v = get_vpe(index)) == NULL)
            return NULL;

      return v->cwd;
}

EXPORT_SYMBOL(vpe_getcwd);

#ifdef CONFIG_MIPS_APSP_KSPD
static void kspd_sp_exit( int sp_id)
{
      cleanup_tc(get_tc(sp_id));
}
#endif

static ssize_t store_kill(struct device *dev, struct device_attribute *attr,
                    const char *buf, size_t len)
{
      struct vpe *vpe = get_vpe(tclimit);
      struct vpe_notifications *not;

      list_for_each_entry(not, &vpe->notify, list) {
            not->stop(tclimit);
      }

      release_progmem(vpe->load_addr);
      cleanup_tc(get_tc(tclimit));
      vpe_stop(vpe);
      vpe_free(vpe);

      return len;
}

static ssize_t show_ntcs(struct device *cd, struct device_attribute *attr,
                   char *buf)
{
      struct vpe *vpe = get_vpe(tclimit);

      return sprintf(buf, "%d\n", vpe->ntcs);
}

static ssize_t store_ntcs(struct device *dev, struct device_attribute *attr,
                    const char *buf, size_t len)
{
      struct vpe *vpe = get_vpe(tclimit);
      unsigned long new;
      char *endp;

      new = simple_strtoul(buf, &endp, 0);
      if (endp == buf)
            goto out_einval;

      if (new == 0 || new > (hw_tcs - tclimit))
            goto out_einval;

      vpe->ntcs = new;

      return len;

out_einval:
      return -EINVAL;;
}

static struct device_attribute vpe_class_attributes[] = {
      __ATTR(kill, S_IWUSR, NULL, store_kill),
      __ATTR(ntcs, S_IRUGO | S_IWUSR, show_ntcs, store_ntcs),
      {}
};

static void vpe_device_release(struct device *cd)
{
      kfree(cd);
}

struct class vpe_class = {
      .name = "vpe",
      .owner = THIS_MODULE,
      .dev_release = vpe_device_release,
      .dev_attrs = vpe_class_attributes,
};

struct device vpe_device;

static int __init vpe_module_init(void)
{
      unsigned int mtflags, vpflags;
      unsigned long flags, val;
      struct vpe *v = NULL;
      struct tc *t;
      int tc, err;

      if (!cpu_has_mipsmt) {
            printk("VPE loader: not a MIPS MT capable processor\n");
            return -ENODEV;
      }

      if (vpelimit == 0) {
            printk(KERN_WARNING "No VPEs reserved for AP/SP, not "
                   "initializing VPE loader.\nPass maxvpes=<n> argument as "
                   "kernel argument\n");

            return -ENODEV;
      }

      if (tclimit == 0) {
            printk(KERN_WARNING "No TCs reserved for AP/SP, not "
                   "initializing VPE loader.\nPass maxtcs=<n> argument as "
                   "kernel argument\n");

            return -ENODEV;
      }

      major = register_chrdev(0, module_name, &vpe_fops);
      if (major < 0) {
            printk("VPE loader: unable to register character device\n");
            return major;
      }

      err = class_register(&vpe_class);
      if (err) {
            printk(KERN_ERR "vpe_class registration failed\n");
            goto out_chrdev;
      }

      device_initialize(&vpe_device);
      vpe_device.class  = &vpe_class,
      vpe_device.parent = NULL,
      strlcpy(vpe_device.bus_id, "vpe1", BUS_ID_SIZE);
      vpe_device.devt = MKDEV(major, minor);
      err = device_add(&vpe_device);
      if (err) {
            printk(KERN_ERR "Adding vpe_device failed\n");
            goto out_class;
      }

      local_irq_save(flags);
      mtflags = dmt();
      vpflags = dvpe();

      /* Put MVPE's into 'configuration state' */
      set_c0_mvpcontrol(MVPCONTROL_VPC);

      /* dump_mtregs(); */

      val = read_c0_mvpconf0();
      hw_tcs = (val & MVPCONF0_PTC) + 1;
      hw_vpes = ((val & MVPCONF0_PVPE) >> MVPCONF0_PVPE_SHIFT) + 1;

      for (tc = tclimit; tc < hw_tcs; tc++) {
            /*
             * Must re-enable multithreading temporarily or in case we
             * reschedule send IPIs or similar we might hang.
             */
            clear_c0_mvpcontrol(MVPCONTROL_VPC);
            evpe(vpflags);
            emt(mtflags);
            local_irq_restore(flags);
            t = alloc_tc(tc);
            if (!t) {
                  err = -ENOMEM;
                  goto out;
            }

            local_irq_save(flags);
            mtflags = dmt();
            vpflags = dvpe();
            set_c0_mvpcontrol(MVPCONTROL_VPC);

            /* VPE's */
            if (tc < hw_tcs) {
                  settc(tc);

                  if ((v = alloc_vpe(tc)) == NULL) {
                        printk(KERN_WARNING "VPE: unable to allocate VPE\n");

                        goto out_reenable;
                  }

                  v->ntcs = hw_tcs - tclimit;

                  /* add the tc to the list of this vpe's tc's. */
                  list_add(&t->tc, &v->tc);

                  /* deactivate all but vpe0 */
                  if (tc >= tclimit) {
                        unsigned long tmp = read_vpe_c0_vpeconf0();

                        tmp &= ~VPECONF0_VPA;

                        /* master VPE */
                        tmp |= VPECONF0_MVP;
                        write_vpe_c0_vpeconf0(tmp);
                  }

                  /* disable multi-threading with TC's */
                  write_vpe_c0_vpecontrol(read_vpe_c0_vpecontrol() & ~VPECONTROL_TE);

                  if (tc >= vpelimit) {
                        /*
                         * Set config to be the same as vpe0,
                         * particularly kseg0 coherency alg
                         */
                        write_vpe_c0_config(read_c0_config());
                  }
            }

            /* TC's */
            t->pvpe = v;      /* set the parent vpe */

            if (tc >= tclimit) {
                  unsigned long tmp;

                  settc(tc);

                  /* Any TC that is bound to VPE0 gets left as is - in case
                     we are running SMTC on VPE0. A TC that is bound to any
                     other VPE gets bound to VPE0, ideally I'd like to make
                     it homeless but it doesn't appear to let me bind a TC
                     to a non-existent VPE. Which is perfectly reasonable.

                     The (un)bound state is visible to an EJTAG probe so may
                     notify GDB...
                  */

                  if (((tmp = read_tc_c0_tcbind()) & TCBIND_CURVPE)) {
                        /* tc is bound >vpe0 */
                        write_tc_c0_tcbind(tmp & ~TCBIND_CURVPE);

                        t->pvpe = get_vpe(0);   /* set the parent vpe */
                  }

                  /* halt the TC */
                  write_tc_c0_tchalt(TCHALT_H);
                  mips_ihb();

                  tmp = read_tc_c0_tcstatus();

                  /* mark not activated and not dynamically allocatable */
                  tmp &= ~(TCSTATUS_A | TCSTATUS_DA);
                  tmp |= TCSTATUS_IXMT;   /* interrupt exempt */
                  write_tc_c0_tcstatus(tmp);
            }
      }

out_reenable:
      /* release config state */
      clear_c0_mvpcontrol(MVPCONTROL_VPC);

      evpe(vpflags);
      emt(mtflags);
      local_irq_restore(flags);

#ifdef CONFIG_MIPS_APSP_KSPD
      kspd_events.kspd_sp_exit = kspd_sp_exit;
#endif
      return 0;

out_class:
      class_unregister(&vpe_class);
out_chrdev:
      unregister_chrdev(major, module_name);

out:
      return err;
}

static void __exit vpe_module_exit(void)
{
      struct vpe *v, *n;

      list_for_each_entry_safe(v, n, &vpecontrol.vpe_list, list) {
            if (v->state != VPE_STATE_UNUSED) {
                  release_vpe(v);
            }
      }

      device_del(&vpe_device);
      unregister_chrdev(major, module_name);
}

module_init(vpe_module_init);
module_exit(vpe_module_exit);
MODULE_DESCRIPTION("MIPS VPE Loader");
MODULE_AUTHOR("Elizabeth Oldham, MIPS Technologies, Inc.");
MODULE_LICENSE("GPL");

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